Can you email me a photo of the part and a copy of your receipt? We can then get you set up to send a replacement. This part would generally be damaged in the following two scenarios-
1) It wasn't fully seated so it spun and the friction tore it, be sure it is pushed all the way into the socket, this involves pushing it in with a pen, dowel, butt of a small file or screwdriver, before inserting the impeller.
2) At some point the drive unit seized to the bushing from fine debris or calcium and spun it. If the calcium level is very high or it is near the discharge of a kalk dower or Ca reactor, this is fairly probable, otherwise this level of calcium build up generally takes at least 6 months.
email is tunze at sbcglobal dot net